What causes Earthquakes

Figuring out the cause of earthquakes has puzzled scientists for centuries.  In fact, today they still only have theories about the exact cause of earthquakes.  While they know a lot about the general cause of earthquakes, they know very little about their precise origins.

In general, earthquakes are caused by a process known as faulting.  Faulting is a sudden side-to-side or vertical movement of the tectonic plates along a break in the Earth’s surface.

In order to understand this, it is important to understand that the surface of the Earth is not a solid surface.  Instead, it is covered in several tectonic plates.  These plates cover the whole Earth, but they are not immobile.  In fact, the study of the movement of these plates is called plate tectonics.

No one is entirely sure why these plates move, but it is commonly believed that their motion is linked with the movement of rock and metal beneath the Earth’s surface.  What is known is where the divides, or faults, between these plates are located.  By tracking areas where earthquake activity is most intense, scientists have been able to identify major and minor fault lines such as the San Andreas Fault in California, the Peru-Chile Trench along the western border of South America and the Mid-Atlantic Ridge.

The tectonic plates are not completely separate from each other.  In fact, most of them have had rock form between their edges over millions of years.  At the fault lines the motion between the plates is not smooth.  As the plates move against each other the strain in the rock that they share builds up.  Eventually, the rocks reach a point where these rocks cannot withstand any more stress and strain. Eventually, the rock breaks apart and the two plates move. What is referred to as an earthquake is the shaking that occurs from the breaking rock.

Plates do not always move apart from each other, but when they do the result is a gash or rift in the Earth.  The most famous of these is along the San Andreas Fault in California.  In some cases, the plates are actually pushing together.  When this happens, a new mountain range can form.  Still, other earthquakes are the result of plates moving alongside each other.  The effects of this movement can be astonishing.  In some cases, surveyors have found that mountains have grown by as much as eighteen inches, while rifts have formed that were over two feet wide.